/* 
 * FreeModbus Libary: A portable Modbus implementation for Modbus ASCII/RTU.
 * Copyright (c) 2006-2018 Christian Walter <cwalter@embedded-solutions.at>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

/* ----------------------- System includes ----------------------------------*/
#include "stdlib.h"
#include "string.h"

#include "../include/mb.h"
#include "../include/mbframe.h"
#include "../include/mbproto.h"
#include "../include/mbconfig.h"

/* ----------------------- Defines ------------------------------------------*/
#define MB_PDU_FUNC_READ_ADDR_OFF           ( MB_PDU_DATA_OFF )
#define MB_PDU_FUNC_READ_DISCCNT_OFF        ( MB_PDU_DATA_OFF + 2 )
#define MB_PDU_FUNC_READ_SIZE               ( 4 )
#define MB_PDU_FUNC_READ_DISCCNT_MAX        ( 0x07D0 )

/* ----------------------- Static functions ---------------------------------*/
eMBException    prveMBError2Exception( eMBErrorCode eErrorCode );

/* ----------------------- Start implementation -----------------------------*/

#if MB_FUNC_READ_COILS_ENABLED > 0
eMBException WHT_MB_Func_Read_Discrete_Inputs(uint8_t* pucFrame, uint16_t* usLen)
{
    uint16_t          usRegAddress;
    uint16_t          usDiscreteCnt;
    uint8_t           ucNBytes;
    uint8_t          *pucFrameCur;

    eMBException    eStatus = MB_EX_NONE;
    eMBErrorCode    eRegStatus;

    if( *usLen == ( MB_PDU_FUNC_READ_SIZE + MB_PDU_SIZE_MIN ) )
    {
        usRegAddress = ( uint16_t )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF] << 8 );
        usRegAddress |= ( uint16_t )( pucFrame[MB_PDU_FUNC_READ_ADDR_OFF + 1] );
        usRegAddress++;

        usDiscreteCnt = ( uint16_t )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF] << 8 );
        usDiscreteCnt |= ( uint16_t )( pucFrame[MB_PDU_FUNC_READ_DISCCNT_OFF + 1] );

        /* 检查要读取的寄存器数量是否有效。如果无效，返回Modbus非法数据值异常。 */
        if((usDiscreteCnt >= 1) && (usDiscreteCnt < MB_PDU_FUNC_READ_DISCCNT_MAX))
        {
            /* 将当前的PDU数据指针设置到起始位置。 */
            pucFrameCur = &pucFrame[MB_PDU_FUNC_OFF];
            *usLen = MB_PDU_FUNC_OFF;

            /* 第一个字节包含功能代码。 */
            *pucFrameCur++ = MB_FUNC_READ_DISCRETE_INPUTS;
            *usLen += 1;

            /* 测试线圈的数量是否为8的倍数。如果不是，最后一个字节仅部分填充，未使用的线圈设为零。 */
            if( ( usDiscreteCnt & 0x0007 ) != 0 )
            {
                ucNBytes = ( uint8_t ) ( usDiscreteCnt / 8 + 1 );
            }
            else
            {
                ucNBytes = ( uint8_t ) ( usDiscreteCnt / 8 );
            }
            *pucFrameCur++ = ucNBytes;
            *usLen += 1;

            eRegStatus = WHT_MB_RegDiscrete_Callback(pucFrameCur, usRegAddress, usDiscreteCnt);

            /* 如果发生错误，将其转换为Modbus异常。 */
            if( eRegStatus != MB_ENOERR )
            {
                eStatus = prveMBError2Exception( eRegStatus );
            }
            else
            {
                /* 响应包含函数代码、起始地址和寄存器数量。我们复用缓冲区中的旧值，因为它们仍然有效。 */
                *usLen += ucNBytes;;
            }
        }
        else
        {
            eStatus = MB_EX_ILLEGAL_DATA_VALUE;
        }
    }
    else
    {
        /* 这不可能是一个有效的读取线圈寄存器请求，因为长度不正确。 */
        eStatus = MB_EX_ILLEGAL_DATA_VALUE;
    }
    return eStatus;
}
#endif
